Congregational Prayer and Its Virtue
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 57
وَقَالَ عَلَيْهِ اَلسَّلاَمُ: «اَلْأَغْلَفُ لاَ يَؤُمُّ اَلْقَوْمَ وَ لَوْ كَانَ أَقْرَأَهُمْ لِلْقُرْآنِ لِأَنَّهُ ضَيَّعَ مِنَ اَلسُّنَّةِ أَعْظَمَهَا وَ لاَ تُقْبَلُ لَهُ شَهَادَةٌ وَ لاَ يُصَلَّى عَلَيْهِ إِلاَّ أَنْ يَكُونَ تَرَكَ ذَلِكَ خَوْفاً عَلَى نَفْسِهِ.
Imam عليه السلام said: "An uncircumcised man (al-aghlaf) should not lead the people in prayer, even if he is the most proficient in reciting the Qur'an among them, because he has neglected one of the greatest aspects of the Sunnah. His testimony is not accepted, and prayers are not performed over him unless he left it (circumcision) out of fear for his life."
- Ṣaḥīḥ al-Faqīh